Packet sending method and network device

ABSTRACT

The present invention provides a packet sending method and a network device. The packet sending method includes: receiving, by a network device, a first data packet; and if a MAC entry matching a destination MAC address of the first data packet is not found in a media access control MAC address table of the network device, sending, by the network device, the first data packet according to a forwarding behavior in a MAC default entry of the MAC address table. When the MAC entry matching the destination MAC address of the first data packet is not found, the network device does not need to flood the first data packet on all interfaces, but directly sends the first data packet according to the MAC default entry in the own MAC address table, thereby reducing a need for MAC address capacity in the network device, and not increasing unnecessary network traffic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201210039629.8, filed on Feb. 21, 2012, which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

The present invention relates to communications technologies, and inparticular, to a packet sending method and a network device.

BACKGROUND

In the prior art, when a packet is forwarded, layer two forwarding isguided according to exact matching of a media access control (MediaAccess Control; hereinafter referred to as MAC) address. When the packetis forwarded in Ethernet (Ethernet), the packet is forwarded to allinterfaces in an unknown unicast flooding (Flooding) way if a matchingMAC entry does not exist, thereby achieving a final effect for sendingthe packet to a destination.

The basic idea for an Ethernet virtual private network (Ethernet VirtualPrivate Network; hereinafter referred to as EVPN) is to learn the MACaddress on a control plane by expanding a border gateway protocol(Border Gateway Protocol; hereinafter referred to as BGP) protocol,thereby realizing a function of layer two VPN (Layer two VPN;hereinafter referred to as L2VPN). Learning the MAC address on thecontrol plane naturally solves the problems caused by performing MACaddress learning on a data plane, such as difficulty to realizemulti-homing of customer edge (Customer Edge; hereinafter referred to asCE) device, unknown unicast Flooding and address resolution protocol(Address Resolution Protocol; hereinafter referred to as ARP)broadcasting storm. However, with the development of cloud computing,the scale of a data center is expanding continuously, but the way forthe EVPN to learn the MAC address on the control plane needs eachprovider edge (Provider Edge; hereinafter referred to as PE) device tostore MAC address tables of all connected VPN sites, which needs veryhigh capacity and performance of the PE device.

However, if a capacity limit is taken into account, and an overall MACaddress table is not stored on a network device (for example, a PEdevice), when the packet is forwarded, the packet may be flooded on allinterfaces if a MAC entry matching a destination MAC address of thepacket does not exist in the MAC address table, but unnecessary networktraffic may therefore be increased.

SUMMARY

The present invention provides a packet sending method and a networkdevice, so as to reduce a need for MAC address capacity in the networkdevice and save network traffic.

In one aspect, the present invention provides a packet sending method,including:

receiving, by a network device, a first data packet; and

if a MAC entry matching a destination MAC address of the first datapacket is not found in a media access control MAC address table of thenetwork device, sending, by the network device, the first data packetaccording to a forwarding behavior in a MAC default entry of the MACaddress table.

In another aspect, the present invention provides a network device,including:

a receiving module, configured to receive a first data packet;

a determining module, configured to determine that a MAC entry matchinga destination MAC address of the first data packet is not found in amedia access control MAC address table of the network device; and

a sending module, configured to send the first data packet according toa forwarding behavior in a MAC default entry of the MAC address table.

In one aspect, the technical effect of the present invention is asfollows: after the first data packet is received, the network devicesends the first data packet according to the forwarding behavior in theMAC default entry of the MAC address table if the MAC entry matching thedestination MAC address of the first data packet is not found in the MACaddress table of the network device. In the present invention, when theMAC entry matching the destination MAC address of the first data packetis not found, the network device does not need to flood the first datapacket on all interfaces, but directly sends the first data packetaccording to the MAC default entry in the own MAC address table, therebyreducing a need for MAC address capacity in the network device, and notincreasing unnecessary network traffic.

In another aspect, the technical effect of the present invention is asfollows: after the receiving module receives the first data packet, thesending module sends the first data packet according to the forwardingbehavior in the MAC default entry of the above-mentioned MAC addresstable if the determining module determines that the MAC entry matchingthe destination MAC address of the first data packet is not found in theMAC address table of the network device. In the present invention, whenthe MAC entry matching the destination MAC address of the first datapacket is not found, the network device does not need to flood the firstdata packet on all interfaces, but directly sends the first data packetaccording to the MAC default entry in the own MAC address table, therebyreducing a need for MAC address capacity in the network device, and notincreasing unnecessary network traffic.

BRIEF DESCRIPTION OF DRAWINGS

To illustrate the technical solutions in the embodiments of the presentinvention or in the prior art more clearly, the following brieflydescribes the accompanying drawings needed for describing theembodiments or the prior art. Apparently, the accompanying drawings inthe following description show some embodiments of the presentinvention, and persons skilled in the art may derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a flow chart of an embodiment of a packet sending method ofthe present invention;

FIG. 2 is a flow chart of another embodiment of the packet sendingmethod of the present invention;

FIG. 3 is a flow chart of still another embodiment of the packet sendingmethod of the present invention;

FIG. 4 is a schematic structural diagram of an embodiment of a networkdevice of the present invention;

FIG. 5 is a schematic structural diagram of another embodiment of thenetwork device of the present invention; and

FIG. 6 is a schematic structural diagram of still another embodiment ofthe network device of the present invention.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of theembodiments of present invention more comprehensible, the followingclearly and completely describes the technical solutions according tothe embodiments of the present invention with reference to theaccompanying drawings in the embodiments of the present invention.Apparently, the embodiments in the following description are merely apart rather than all of the embodiments of the present invention. Allother embodiments obtained by persons skilled in the art based on theembodiments of the present invention without creative efforts shall fallwithin the protection scope of the present invention.

FIG. 1 is a flow chart of an embodiment of a packet sending method ofthe present invention, and as shown in FIG. 1, the packet sending methodmay include:

Step 101: A network device receives a first data packet.

Step 102: If a MAC entry matching a destination MAC address of the firstdata packet is not found in a MAC address table of the network device,the network device sends the first data packet according to a forwardingbehavior in a MAC default entry of the MAC address table.

In this embodiment, the MAC default entry is used to indicate theforwarding behavior when the MAC entry matching the destination MACaddress of the data packet received by the network device is not foundin the MAC address table; the MAC address in the MAC default entry is adefault MAC address, and a value of each bit of the default MAC addressis 0. The MAC default entry is used to indicate a forwarding path whenthe destination MAC address of the data packet received by the networkdevice is not in the own MAC address table, and the forwarding path is aspecial forwarding path. Simply, the MAC default entry is the MAC entryused by the network device when the MAC entry matching the destinationMAC address is not found. In the MAC address table, the MAC address inthe MAC default entry is the default MAC address which appears in theform of all 0.

In an implementation manner of this embodiment, the network device maybe a PE device. In the implementation manner, before the step 101, thePE device may receive an update message sent by a route reflector (RouteReflector; hereinafter referred to as RR) at first, the update messagesent by the RR carries network layer reachability information (NetworkLayer Reachability Information; hereinafter referred to as NLRI), a nexthop address and a route target (Route Target; hereinafter referred to asRT) attribute, where the NLRI includes a default MAC address, the nexthop address is an address of the RR, the RT attribute is used toidentify a VPN that the default MAC address belongs to, and for example,the default MAC address may be included in a MAC address (MAC Address)field of the NLRI.

Then, the PE device may determine a tunnel between the PE device and theRR according to the next hop address, and generate, according to theNLRI and the next hop address, the MAC default entry of the VPNidentified by the RT attribute, where the forwarding behavior in the MACdefault entry of the VPN includes sending, via the tunnel between the PEdevice and the RR, the data packet received by the PE device to the RR;for example, after the tunnel is established between the PE device andthe RR, the PE device may find the forwarding path (that is, routeiteration) of the next hop according to the next hop address, and thenmay find the tunnel between the PE device and the RR, thereby maydetermine the tunnel between the PE device and the RR. After the tunnelbetween the PE device and the RR is determined according to the next hopaddress, the PE device may generate, according to the NLRI and the nexthop address, the MAC default entry of the VPN identified by the RTattribute, where the MAC address in the default entry of the VPN is thedefault MAC address, and the forwarding behavior in the default entry ofthe VPN is sending, via the tunnel between the PE and the RR, the datapacket of the VPN received by the PE device to the RR.

Finally, the PE device stores the MAC default entry of the VPN into theMAC address table of the PE device. For example, while storing the MACdefault entry of the VPN, the PE device may store the MAC default entryof the VPN into a fixed special position of the MAC address table of thePE device, such as a first or last position of the MAC address table.

In the implementation manner, the step 102 may be as follows: the PEdevice sends the first data packet to the RR via the tunnel between thePE device and the RR, so that after finding, in the MAC address table ofthe RR, a first MAC entry matching the destination MAC address of thefirst data packet, the RR sends, according to the first MAC entry, thefirst data packet to the PE device accessed by a VPN site that thedestination MAC address belongs to.

In another implementation manner of this embodiment, the network devicemay be a first switching device. In the implementation manner, beforethe step 101, the first switching device may further configure the MACdefault entry in the MAC address table of the first switching device,the forwarding behavior in the MAC default entry includes sending thedata packet received by the first switching device to an upper-layerswitching device of the first switching device, and the MAC address inthe MAC default entry is the default MAC address. In hierarchicalstructure networking, a switching device with lower capacity andperformance is usually placed on a lower layer, and a switching devicewith higher capacity and performance is placed on an upper layer. In thepresent invention, the switching device placed on the lower layer iscalled a lower-layer switching device, and the switching device placedon the upper layer is called an upper-layer switching device; and oneupper-layer switching device may be connected to a plurality oflower-layer switching devices to implement the functions ofhigh-capacity user accessing and high-performance forwarding together.

In the implementation manner, the step 102 may be as follows: the firstswitching device sends the first data packet to the upper-layerswitching device of the first switching device according to theforwarding behavior in the MAC default entry.

In the embodiment, after the first data packet is received, the networkdevice sends the first data packet according to the forwarding behaviorin the MAC default entry of the MAC address table if the MAC entrymatching the destination MAC address of the first data packet is notfound in the MAC address table of the network device. In the embodiment,when the MAC entry matching the destination MAC address of the firstdata packet is not found, the network device does not need to flood thefirst data packet on all interfaces, but directly sends the first datapacket according to the MAC default entry in the own MAC address table,thereby reducing a need for MAC address capacity in the network device,and not increasing unnecessary network traffic.

In the method provided by the embodiment as shown in FIG. 1, the MACdefault entry is stored in the MAC address table of the network device.When the data packet arrives at the network device, if the networkdevice does not find, in the own MAC address table, the MAC entrymatching the destination MAC address of the data packet, the networkdevice does not flood on all interface according to the usual forwardingprinciple of Ethernet, but sends the data packet according to theforwarding behavior in the MAC default entry. The present inventiongreatly saves the need for MAC address capacity in the network device,does not increase the unnecessary network traffic, and may furtherimprove networking flexibility of the network devices with differenthardware capabilities.

FIG. 2 is a flow chart of another embodiment of a packet sending methodof the present invention, and as shown in FIG. 2, the packet sendingmethod may include:

Step 201: The PE device receives a BGP update packet sent by the RR,where the BGP update packet carries an NLRI, a next hop address and anRT attribute.

The NLRI includes a default MAC address, namely, the MAC address withall 0 in each bit; for example, the default MAC address may be includedin the MAC address (MAC Address) field of the NLRI; the next hop addressis an address of the RR, such as an Internet protocol (InternetProtocol; hereinafter referred to as IP) address of the RR; and the RTattribute is used to identify a VPN that the default MAC address belongsto.

Step 202: The PE device determines a tunnel between the PE device andthe RR according to the next hop address.

For example, after the tunnel between the PE device and the RR isestablished, the PE device may find the forwarding path (that is, routeiteration) of the next hop according to the next hop address, and thenmay find the tunnel between the PE device and the RR, thereby maydetermine the tunnel between the PE device and the RR.

Step 203: The PE device generates, according to the NLRI and the nexthop address, the MAC default entry of the VPN identified by the RTattribute, where the forwarding behavior in the default entry of the VPNincludes sending, via the tunnel between the PE device and the RR, thedata packet received by the PE device to the RR.

For example, after the tunnel between the PE device and the RR isdetermined according to the next hop address, the PE device maygenerate, according to the NLRI and the next hop address, the MACdefault entry of the VPN identified by the RT attribute, the MAC addressin the default entry of the VPN is the default MAC address, and theforwarding behavior in the default entry of the VPN is sending, via thetunnel between the PE and the RR, the data packet of the VPN received bythe PE device to the RR.

In this embodiment, the MAC default entry of the VPN is used to indicatethe forwarding behavior when the MAC entry matching the destination MACaddress of the data packet of the VPN received by the network device isnot found in the MAC address table; the MAC address in the MAC defaultentry of the VPN includes a default MAC address, and a value of each bitof the default MAC address is 0, namely, the default MAC address appearsin the form of all 0. The MAC default entry of the VPN is used toindicate a forwarding path when the destination MAC address of the datapacket of the VPN received by the network device is not in the own MACaddress table, and the forwarding path is a special forwarding path.Simply, the MAC default entry of the VPN is the MAC entry used by thenetwork device when the MAC entry matching the destination MAC addressis not found.

Step 204: The PE device stores the MAC default entry of the VPN into theMAC address table of the PE device.

For example, while storing the MAC default entry of the VPN, the PEdevice may store the MAC default entry of the VPN into a fixed specialposition of the MAC address table of the PE device, such as a first orlast position of the MAC address table.

Step 205: The PE device receives the first data packet of the VPN.

Step 206: The PE device sends the first data packet to the RR via thetunnel between the PE device and the RR according to the forwardingbehavior in the MAC default entry of the VPN if the PE device determinesthat the MAC entry matching the destination MAC address of the firstdata packet is not found in the own MAC address table and determinesthat the MAC default entry of the VPN is found in the MAC address table.

Step 207: After finding, in the MAC address table of the RR, a first MACentry matching the destination MAC address of the first data packet, theRR sends, according to the first MAC entry, the first data packet to thePE device accessed by the VPN site that the destination MAC addressbelongs to.

In this embodiment, the subsequent data packet sent to the destinationMAC address is in the MAC address table of the PE device after the PEdevice learns the destination MAC address of the first data packet via acontrol plane or data plane, so that the MAC entry matching thedestination MAC address may be directly found, in this way, the PEdevice may forward subsequent data packet according to the MAC entrymatching the destination MAC address without using the MAC defaultentry.

In the embodiment, when the MAC entry matching the destination MACaddress of the first data packet is not found, the PE device does notneed to flood the first data packet on all interfaces, but directlysends the first data packet according to the MAC default entry in theown MAC address table, thereby reducing a need for MAC address capacityin the PE device, and not increasing unnecessary network traffic.

FIG. 3 is a flow chart of still another embodiment of a packet sendingmethod of the present invention, and this embodiment introduces a packetsending method in a networking scheme of learning a MAC address on adata plane.

As shown in FIG. 3, the packet sending method may include:

Step 301: Configure a MAC default entry in a MAC address table of alower-layer switching device.

Specifically, in hierarchical structure networking, the switching devicewith lower capacity and performance is usually placed on the lowerlayer, and the switching device with higher capacity and performance isplaced on the upper layer. In the present invention, the switchingdevice placed on the lower layer is called a lower-layer switchingdevice, and the switching device placed on the upper layer is called anupper-layer switching device; and one upper-layer switching device maybe connected to a plurality of lower-layer switching devices toimplement the functions of high-capacity user accessing andhigh-performance forwarding together. Because the performance andcapacity of the lower-layer switching device are lower, in thisembodiment, the lower-layer switching device may be configured not tolearn all of the MAC addresses, but the MAC default entry is configuredin the MAC address table of the lower-layer switching device. Theforwarding behavior in the MAC default entry includes sending the datapacket received by the lower-layer switching device to the upper-layerswitching device connected to the lower-layer switching device, wherethe MAC address in the MAC default entry is the default MAC address.

Step 302: The lower-layer switching device receives the data packet.

Step 303: If the lower-layer switching device determines that the MACentry matching the destination MAC address of the data packet is notfound in the own MAC address table and determines that the MAC defaultentry is found in the MAC address table, the lower-layer switchingdevice sends, according to the forwarding behavior in the MAC defaultentry, the data packet to the upper-layer switching device connected tothe lower-layer switching device.

Step 304: The upper-layer switching device forwards the data packetaccording to the MAC address table of the upper-layer switching device.

In the embodiment, when the MAC entry matching the destination MACaddress of the data packet is not found, the lower-layer switchingdevice does not need to flood the data packet on all interfaces, butdirectly sends the data packet according to the MAC default entry in theown MAC address table, thereby reducing a need for MAC address capacityin the lower-layer switching device, and not increasing unnecessarynetwork traffic.

Persons skilled in the art may understand that all or part of the stepsof the method according to the embodiments of the present invention maybe implemented by a program instructing relevant hardware. Theaforementioned program may be stored in a computer-readable storagemedium. The steps including each of the method embodiments are performedwhile the program is performed; and the aforementioned medium includesvarious mediums capable of storing program codes, such as a ROM, a RAM,a disk or a compact disc.

FIG. 4 is a schematic structural diagram of an embodiment of a networkdevice of the present invention. The network device in this embodimentmay realize the process of the embodiment as shown in FIG. 1 in thepresent invention, and as shown in FIG. 4, the network device mayinclude a receiving module 41, a determining module 42 and a sendingmodule 43;

the receiving module 41 is configured to receive a first data packet;

the determining module 42 is configured to determine that a MAC entrymatching a destination MAC address of the first data packet is not foundin a MAC address table of the network device; and

the sending module 43 is configured to send the first data packetaccording to a forwarding behavior in a MAC default entry of the MACaddress table.

In this embodiment, the MAC default entry is used to indicate theforwarding behavior when the MAC entry matching the destination MACaddress of the data packet received by the network device is not foundin the MAC address table; the MAC address in the MAC default entryincludes a default MAC address, and a value of each bit of the defaultMAC address is 0. The MAC default entry is used to indicate a forwardingpath when the destination MAC address of the data packet received by thenetwork device is not in the own MAC address table, and the forwardingpath is a special forwarding path. Simply, the MAC default entry is theMAC entry used by the network device when the MAC entry matching thedestination MAC address is not found. In the MAC address table, the MACaddress in the MAC default entry is the default MAC address whichappears in the form of all 0.

In this embodiment, the network device may be the network device forsending the packet according to the MAC address table, such as aswitching device or a PE device. The present invention does not limitthe specific form of the network device.

In the network device, after the receiving module 41 receives the firstdata packet, the sending module 43 sends the first data packet accordingto the forwarding behavior in the MAC default entry of the MAC addresstable when the determining module 42 determines that the MAC entrymatching the destination MAC address of the first data packet is notfound in the MAC address table of the network device. In thisembodiment, when the MAC entry matching the destination MAC address ofthe first data packet is not found, the network device does not need toflood the first data packet on all interfaces, but directly sends thefirst data packet according to the MAC default entry in the own MACaddress table, thereby reducing a need for MAC address capacity in thenetwork device, and not increasing unnecessary network traffic.

FIG. 5 is a schematic structural diagram of another embodiment of anetwork device of the present invention. The network device in thisembodiment may be a PE device, and comparing with the network device asshown in FIG. 4, a difference is that the network device shown in FIG. 5may further include a generating module 44 and a storing module 45;

in this embodiment, the receiving module 41 is further configured toreceive an update message sent by a RR, where the update message sent bythe RR carries an NLRI, a next hop address and an RT attribute, the NLRIincludes a default MAC address, the next hop address is an address ofthe RR, and the RT attribute is used to identify a VPN that the defaultMAC address belongs to;

the determining module 42 is further configured to determine a tunnelbetween the network device and the RR according to the next hop address;

the generating module 44 is configured to generate, according to theNLRI and the next hop address, the MAC default entry of the VPNidentified by the RT attribute, where the forwarding behavior in thedefault entry of the VPN includes sending, via the tunnel between thenetwork device and the RR, the data packet received by the networkdevice to the RR; and

the storing module 45 is configured to store the MAC default entry ofthe VPN into the MAC address table of the network device; for example,while storing the MAC default entry of the VPN, the storing module 45may store the MAC default entry of the VPN into a fixed special positionof the MAC address table of the network device, such as a first or lastposition of the MAC address table.

For example, the sending module 43 may send the first data packet to theRR via the tunnel between the PE device and the RR, so that afterfinding, in the MAC address table of the RR, a first MAC entry matchingthe destination MAC address of the first data packet, the RR sends,according to the first MAC entry, the first data packet to the PE deviceaccessed by a VPN site that the destination MAC address belongs to.

In the embodiment, when the MAC entry matching the destination MACaddress of the first data packet is not found, the network device doesnot need to flood the first data packet on all interfaces, but directlysends the first data packet according to the MAC default entry in theown MAC address table, thereby reducing a need for MAC address capacityin the network device, and not increasing unnecessary network traffic.

FIG. 6 is a schematic structural diagram of still another embodiment ofa network device of the present invention. The network device in theembodiment may be a switching device, and comparing with the networkdevice as shown in FIG. 4, the difference is that the network device asshown in FIG. 6 may further include a configuring module 46;

the configuring module 46 is configured to configure a MAC default entryin a MAC address table of the network device, where a forwardingbehavior in the MAC default entry includes sending a data packetreceived by the network device to an upper-layer switching deviceconnected to the network device, where the MAC address in the MACdefault entry is the default MAC address.

In this embodiment, specifically, the sending module 43 may send,according to the forwarding behavior in the MAC default entry, the firstdata packet to the upper-layer switching device connected to the networkdevice.

In this embodiment, when the MAC entry matching the destination MACaddress of the first data packet is not found, the network device doesnot need to flood the first data packet on all interfaces, but directlysends the first data packet according to the MAC default entry in theown MAC address table, thereby reducing a need for MAC address capacityin the network device, and not increasing unnecessary network traffic.

It should be understood by persons skilled in the art that theaccompanying drawings are merely schematic diagrams of an exemplaryembodiment, and modules or processes in the accompanying drawings arenot necessarily needed in implementing the present invention.

Those skilled in the art may understand that the modules in the devicesprovided in the embodiments may be arranged in the devices according tothe description of the embodiments, or may be arranged in one ormultiple devices which are different from those described in theembodiments. The modules in the embodiments may be combined into onemodule, or split into multiple submodules.

Finally, it should be noted that the above embodiments are merelyintended for describing the technical solutions of the present inventionother than limiting the present invention. Although the presentinvention is described in detail with reference to the embodiments,persons skilled in the art should understand that they may still makemodifications to the technical solutions described in the embodiments,or make equivalent substitutions to some or all the technical featuresthereof, without departing from the spirit and scope of the technicalsolutions of the embodiments of the present invention.

What is claimed is:
 1. A method performed by a network device forsending a packet, the network device storing a Media Access Control(MAC) address table, wherein the MAC address table includes a MACdefault entry, the MAC default entry including an association between adefault MAC address and a next hop address, wherein the MAC defaultentry is used to indicate a forwarding behavior when the network devicefinds no MAC entry in the MAC address table matching a destination MACaddress of a received data packet, wherein the method comprises:receiving the data packet, the received data packet including thedestination MAC address; determining whether there is a MAC entry in theMAC address table matching the destination MAC address of the datapacket; in response to a determination that there is no MAC entry in theMAC address table matching the destination MAC address of the datapacket, sending the data packet to a network device identified by thenext hop address.
 2. The method according to claim 1, wherein a value ofeach bit of the default MAC address is
 0. 3. The method according toclaim 1, wherein the network device comprises a provider edge (PE)device; before the receiving the data packet, the method furthercomprises: receiving, by the PE device, an update message sent by aroute reflector, wherein the update message sent by the route reflectorcarries network layer reachability information, the next hop address anda route target attribute, wherein the network layer reachabilityinformation comprises the default MAC address, the next hop address isan address of the route reflector, and the route target attribute isused to identify a virtual private network that the default MAC addressbelongs to; determining, by the PE device, a tunnel between the PEdevice and the route reflector according to the next hop address;generating, according to the network layer reachability information andthe next hop address, the MAC default entry of the virtual privatenetwork identified by the route target attribute, wherein the forwardingbehavior indicated by the MAC default entry of the virtual privatenetwork comprises sending, via the tunnel between the PE device and theroute reflector, the data packet received by the PE device to the routereflector; and storing, by the PE device, the MAC default entry of thevirtual private network into the MAC address table of the PE device. 4.The method according to claim 3, wherein the sending the data packetaccording to the forwarding behavior indicated by the MAC default entryin the MAC address table comprises: sending, by the PE device, the datapacket to the route reflector via the tunnel between the PE device andthe route reflector.
 5. The method according to claim 1, wherein thenetwork device comprises a switching device; before the receiving thedata packet, the method further comprises: configuring, by the switchingdevice, the MAC default entry in the MAC address table, wherein theforwarding behavior indicated by the MAC default entry comprises sendingthe data packet received by the switching device to an upper-layerswitching device of the switching device.
 6. The method according toclaim 5, wherein the sending the data packet according to the forwardingbehavior indicated by the MAC default entry in the MAC address tablecomprises: sending, by the switching device, the data packet to theupper-layer switching device of the switching device according to theforwarding behavior indicated by the MAC default entry.
 7. A networkdevice, the network device storing a Media Access Control (MAC) addresstable, wherein the MAC address table includes a MAC default entry, theMAC default entry including an association between a default MAC addressand a next hop address, wherein the MAC default entry is used toindicate a forwarding behavior when the network device finds no MACentry in the MAC address table matching a destination MAC address of areceived data packet, wherein the network device comprises: a receivingmodule, configured to receive the data packet, the received data packetincluding the destination MAC address; a determining module, configuredto determine whether there is a MAC entry in the MAC address tablematching the destination MAC address of the data packet ; and a sendingmodule, configured to send, in response to a determination that there isno MAC entry in the MAC address table matching the destination MACaddress of the data packet, the data packet to a network deviceidentified by the next hop address.
 8. The network device according toclaim 7, further comprising: a generating module and a storing module;wherein the receiving module is further configured to receive an updatemessage sent by a route reflector, wherein the update message sent bythe route reflector carries network layer reachability information, thenext hop address and a route target attribute, wherein the network layerreachability information comprises the default MAC address, the next hopaddress is an address of the route reflector, and the route targetattribute is used to identify a virtual private network that the defaultMAC address belongs to; the determining module is further configured todetermine a tunnel between the network device and the route reflectoraccording to the next hop address; the generating module is configuredto generate, according to the network layer reachability information andthe next hop address, the MAC default entry of the virtual privatenetwork identified by the route destination attribute, wherein theforwarding behavior indicated by the MAC default entry of the virtualprivate network comprises sending, via the tunnel between the networkdevice and the route reflector, the data packet received by the networkdevice to the route reflector; and the storing module is configured tostore the MAC default entry of the virtual private network into the MACaddress table.
 9. The network device according to claim 8, wherein thesending module is configured to send the data packet to the routereflector via the tunnel between the network device and the routereflector according to the forwarding behavior indicated by the MACdefault entry.
 10. The network device according to claim 7, furthercomprising: a configuring module, configured to configure the MACdefault entry in the MAC address table, wherein the forwarding behaviorindicated by the MAC default entry comprises sending the data packetreceived by the network device to an upper-layer switching device of thenetwork device.
 11. The network device according to claim 10, whereinthe sending module is configured to send the data packet to theupper-layer switching device of the network device according to theforwarding behavior indicated by the MAC default entry.
 12. A computerprogram product comprising a non-transitory storage medium storingcomputer executable instructions, wherein the computer executableinstructions cause a network device storing a Media Access Control (MAC)address table to perform a process, wherein the MAC address tableincludes a MAC default entry, the MAC default entry including anassociation between a default MAC address and a next hop address,wherein the MAC default entry is used to indicate a forwarding behaviorwhen the network device finds no MAC entry in the MAC address tablematching a destination MAC address of a received data packet, whereinthe process comprises: receiving the data packet, the received datapacket including the destination MAC address; determining whether thereis a MAC entry in the MAC address table matching the destination MACaddress of the data packet; in response to a determination that there isno MAC entry in the MAC address table matching the destination MACaddress of the data packet, sending the data packet to a network deviceidentified by the next hop address.
 13. The computer program productaccording to claim 12, wherein and a value of each bit of the defaultMAC address is 0.